In response to the increased use of packet-loss sensitive traffic types (such as voice and multimedia) on wireless local area networks (WLANs), the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Taskgroup E (802.11e) added quality of service (QoS) enhancements to the Media Access Control (MAC) layer of the IEEE 802.11 wireless network standard. That standard is currently documented here: IEEE std. 802.11-2007, published Jun. 12, 2007. Those QoS enhancements are part of the IEEE 802.11e amendment (IEEE std. 802.11-1995, published Nov. 11, 2005).
With a desire to increase throughput and range of WLANs, the IEEE Taskgroup N (802.11n) introduced Multiple-Input and Multiple-Output (MIMO) to the IEEE 802.11 standard. With MIMO, multiple receivers and transmitters in both a wireless access point (AP) and a wireless receiving station (STA) improve throughput and range. MIMO is one of the core technologies of the IEEE 802.11n amendment (IEEE std. 802.11-2009, published Oct. 29, 2009). The MIMO of IEEE 802.11n is single-user MIMO (SU-MIMO), where the STA receives the AP's signals via multiple antennas at the same time to improve signal coherence for that STA.